1. Field of the Invention
The present invention relates to a wheel suspension for a wheeled vehicle of the type comprising at least one lower, wheel-carrying radius arm with an inner end, which is designed for fastening so that it can pivot about a substantially horizontal axis to a vehicle frame, and an outer end, which is pivotally connected to a lower part of a wheel hub, and at least one upper support arm, one end of which is fastened to an upper part of the wheel hub, and the other end of which is pivotally connected to a part of the vehicle fixed to the frame. The invention relates in particular, but not exclusively, to such a wheel suspension for relatively large and heavy motor vehicles, in which high ground clearance is desirable. The wheel suspension according to the invention has applications on both steered and unsteered wheels and on driving and non-driving wheels.
2. Related Art
In known wheel suspensions of the aforementioned type, compression and rebound movements of the wheels are often a cause of unwanted changes in the track width and changes in the camber angles of the wheels, which has an adverse effect on the driving characteristics of the vehicle and can lead to unwanted tyre wear.
In order to compensate for such changes in the compression and rebound movements of vehicle wheels, U.S. Pat. No. 3,652,104, for example, proposes an independent wheel suspension, in which a track width reduction occurring in a compression movement is compensated for by increasing the negative camber, the upper fastening point of the wheel being drawn in, so that at the lower edge the wheel is forced outwards away from the centre of the vehicle. In a rebound movement, however, the change in the track width will be greater, since the compensating mechanism tends to increase the positive camber, which draws the wheel in at the bottom edge whilst the geometric path of the suspension arm also draws the wheel in. In the case of long suspension travels, however, large changes in track width occur, for which this increase in the camber cannot compensate.
WO 94/12359 describes a vehicle wheel suspension system, in which the change in track width in a compression movement is compensated for in that control arms, which are seated in rubber bushings, are forced outwards in order to force the wheel out from the centre of the vehicle, thereby compensating for the geometric path of the suspension arm, which draws the wheel in. In the case of a rebound movement, on the other hand, there is no compensation, the wheel conventionally following the geometric path of the suspension arm, that is to say drawing the wheel in towards the centre of the vehicle.
U.S. Pat. No. 5,498,019 further describes a wheel suspension system which compensates for the change in track width in a compression movement in that a link forces the suspension arms and thereby the wheel outwards away from the centre of the vehicle. In the case of a rebound movement, however, the change in track width is pronounced, since both the geometry of the suspension arms and a compensation mechanism draw the wheel in towards the centre of the vehicle.
A common feature of the aforementioned known wheel suspension systems, therefore, is the fact that they do not compensate sufficiently for changes in track width in both compression and rebound movements of the vehicle wheels.